Safety device for elevators



June 17, 1930. R. P. HIGBEE SAFETY DEVICE FOR ELEVATORS Filed May 5. 192a ATTORNEY a modification of the invention illustrated Patented June 17, 1930 UNITED STATES PATENT RAY r. HIGBEE, or PHILVADVEIVJZPHIA, P NNS LV NIA, assrenon ro wnlspprnenousn' ELECTRIC &.MANUFVACTURIIG conraNY, a conroaar o v or rnnnsvnvanre j SAFETY FOR ELEVATORS Application filed ma 9,

My invention relates generally tosafety devices for elevators and more particularly to safety devices forpreventing falling of elevator cars.

i The object of the invention, generally stated, is the provision .of a safety device that shall be simple and efficient in operaiton and adapted for ready and economical manufacture and installation.

A more specific object of myinvention is toprovide for a prompt application of the applied to the gripping jaws of the safety device.

It is also an object of my invention to provide for applying an additional pressure to the gripping jaws when the initial pressure applied thereto is not suflicient to stop the car. Y

The invention, as disclosed in the accompanying drawing, comprises the structural devices and the combination of elements and arrangements of parts which will be hereinafter set forth and particularly-defined in the claims. I

For a fuller understanding of the invention, reference may be had to the following detailed description, taken in connection with the accompanying drawing, in which:

Figure 1 is a diagrammatic representation of the platform of an elevator car provided with a safety device constructed in accordance with my invention, I

Fig. 2 is a diagrammatic representat on of in Fig. 1, and s Fig. 3 is an enlarged top lan view, partially in section, of the sa ety drum emleas, seriaim; 274,765.

bodied in the safety device illustrated in .Figs.1.and.2'.

In the drawing, I have illustrated the platform of an elevator car 1 as mounted between aepair of "guide "rails 2 and 3 and provided with .a safety device having two pairs of cooperating safety jaws 4, 5, 6 and 7 for gripping the guide rails when the safe ty device is actuated. Thesafety jaws 4,

5, 6 and 7 constitute integral parts, of, and are operated by, two pairs of cooperating bell-crank levers 9,910, 11 and 12, thatare pivotally mounted on the underside. of the car floor-:or frame 1 by means of pivotal supports 13,14, '15 and 16. The outer. ends .of the bel1'-crank: lever s 1,0 and 12, as s0- ciatedwith the jaws 5 and 7 on the one side of the guide railsy-ai'iezconnected and held in operative positions byl 1a pair- 0f push rods17 and 18, while the cooperating bell-crank levers 9 and'11, associated with the jaws/1' and (ion the other'side of the gulde rails,.are connected and held in operative positions-by. a pair of push rods 19and20. I 7 .f'

In orderthat the safety jaws 4, 5, 6 and 7 may beiactuatedito grip theguiderails 2 and 3 when the'downwardspe'ed of the car 1 exceeds a predeterminedlimit, a safety drum 21,;isdisposed between the inner ends of the pushrods l9 and 20 for the purpose of moving therods outwardly: The :safety drum 21is mounted on. a frame 22 (see Fig.

3) andisprovidedwitha right-handscrlewthreadedm'ember 26 that engages a' cooperating threaded .portion 27 of a pressuretransmittingmember 28 mounted on the in- :ner end of the pushrod 20, and a leftrhand screw-threaded member .29 that engages a Cooperating threaded portion 30 on the push rod-1.9.. :The pressure-transmitting. member '28 1S: provided withv a separate sleeve portion 31 that fits :over the ends of .the push rod 20 and is secured against. rotation thereon by meansofa-friction clamp.32, for thepurpose thatywillibe hereinafter explained.

Inasmuch asl-the outer ends 0f;the push rods 19 and 20 are square and;are.disposed in square holes, provided in the bell-crank levers ,9 and 11, the-rodswill be prevented from rotating and will be moved away from each other longitudinally when the screwthreaded members 26 and 29 are turned on the threaded portions 27 and 30 by the rotation of the safety drum 21.

The means for rotating the safety drum 21 to operate the push rods comprises a tail rope 35, one end of which is wound around, and secured, to the safety drum and the other end ofwhi'ch is disposed over a pair of guiding sheaves 36 and 37, on the underside of the car platform 1, and is secured to a governor cable (not shown). Inasmuch as governor cables are old and well-known in the art, a description thereof will be omitted. i

As shown, the safety drum 21 is provided with a bevelled gear 38 on its right-hand end by means of which it maybe reset by any suitable resetting tool (not shown) after it has been operated by the movement of the tail rope 35.

Referring to'Fig; 1 of the drawing, in order that the running clearance between the safety jaws 4, 5, 6 and 7 and the guide rails 2 and 3 may be rapidly reduced and the jaws be caused to grip the guide rails'as soon as possible after the operation of the safety device, the screw-threaded member 26 and the cooperating worm 27. areconstructed with arelatively high pitch so that the first fewturns of the safety drum 21 will effect a rapid longitudinal separation of the push rods 19 and 20.

For the purpose of 1 providing a means for cushioning the initial gripping action of the j aws-on the guide rails and also to pro- 'vide for'the application of a predetermined initial pressure to the jaws, a resilient memdistance apart but whichwill, when compressed to a point where the ends of the push rods meet, exert a sufiicient pressure through the push rods, the bell-crank levers and the safety jaws to stop the car.

The frictional clamp 32 that is mounted on the power-transmitting member 28 is provided for'the purpose of preventing that member from rotating with the safety drum 21 until thepressure between the threads on the members 26 and 27 reaches such a degree that the friction caused thereby overcomes the frictional engagement of the clamp and causes the pressure-transmitting member 28 to rotate with the safety drum 21. Inthe present case, the frictional engagement of the clamp 32 is designed to be overcome at the point when the spring 39 is compressed to such degree-that the inner ends of the cooperating push rods 17 and 18 engage each other and cause a positive pressure to be exerted on the safety jaws 4, 5, 6 and 7.

In the modification of the invention illustrated in Fig. 2, the spring 39a is so disposed on the push rods 17 and 18 that it will, unless compressed, close the safety jaws 4, 5, 6 and 7 on the guide rails 2 and 3 with sufficient pressure to stop the car. Therefore, in this modification of the invention, an electromagnet 42 is mounted on the inner ends of the cooperating push rods 17 and 18 in, conjunction with the spring 39a to pull the rods together against the compression of thespring'and thereby maintain a running clearance between the jaws and the 3 guide rails. vOne end of the electromagnet governor 47 in such manner that the downward operation of the'car 1 at an excessive speed will cause thegovernor to open the switch and thereby deenergize the electromagnet 42.

It should be noted that, with the safety device arranged either as shown in Fig. 1 or in Fig. 2, it is necessary to provide for a small transverse movement of the car 1 with reference to the guide rails 2 and 3 for the purpose of permitting full cooperation of the safety jaws 4, 5, 6 and 7.

- The operation of the'safety device, as arranged in Fig. 1, is as follows: Assuming that the car, in traveling downward, exceeds a predetermined speed limit, it will, through the action of the safety governor 47 and the governor cable (not shown), exert a pull on the tail rope 35 which will, in turn, rotate the safety drum 21. The rotation of the safety drum 21 will, through the action of the high-pitch screw-threaded member 26 and the lower-pitch screw-threaded member 29, cause the push rods 19 and 20, to rapidly move outward from the drum and push against the outer arms of the bellcrank levers 9 and 11. The pressure of the theguide rails 2 and 3. The rotation of the safety drum 21 will be continued by the action of the falling car, in pulling on the tailrope 35, until the pressure exerted on the safety jaws is sufficient to stop the car. Under ordinary c1rcumstances,the initial pressure, as determinedby the spring 39, will be sufficient to stop the'car when operating at such speed as will trip the governor, and when normal loads are carried by the car. However, if this pressure is not sufficient to stop the car and the car continues downward, the safety drum 21 will continue to rotate and increase the closing pressure on the jaws at, 5, 6 and 7..

As the pressure increases, the spring 39 will be compressed to a point where the inner ends of the push rods 17 and 18 engage each other and cause a positive application of the closing pressure to the safety jaws. At this stage of the operation, the pressure between the high-pitch screwthreaded member 26 and the screw-threaded worm 27 on the power-transmitting member 28 will create sufficient friction to overcome the frictional engagement of the clamp and cause the member 28 to rotate with the safety drum 21. When the member 28 rotates with the safety drum 21, the additional spreading pressure is effected by the drum through the low-pitch member 29, and the action continues at the low speed of the member 29 until the car stops.

The operation of the modified form of the device illustrated in Fig. 2 is practically the same as that shown in Fig. 1 except that the setting of the safety governor Q? by an excessive downward speed of the car 1 will open the switch 45 and deenergize the electromagnet 42. The deenergization of the electromagnet 12 releases the pushrod 18 and permits the spring 39a to effect a closing movement of the safety jaws 4i, 5, 6 and 7 At the same time, the safety drum 21 starts to rotate and applies an additional closing pressure to the jaws through the outward movement of the push rods 19 and 20. If the car is not stopped by the pressure applied through the initial expansion of the spring 89a, the safety drum will continue to rotate until the spring is compressed to such a point that the inner ends of the push rods 17 and 18 engage each other and cause a positive pressure to be applied to the jaws. If the car is not stopped by the pressure applied at this stage of the operation of the safety device, the further descent of the car continues the rotation of the safety drum 21 and applies additional positive closing pressure to the jaws until the car comes to rest.

hen it is desired to reset the safety device after it has operated to stop the car, any suitable resetting tool (not shown) may be employed to engage the gear teeth 38 on the safety drum 21 and rotate it to re lease the safety jaws 4, 5, 6 and 7 and rewind the tail rope 35 on the drum.

It will, therefore, be seen that I have devised an improved safety device that .pro- VlClGS' for the prompt application of an 1mtial cushioned retarding force upon the op eration of the safety governor; thatl have provided forlimiting the initial retarding force to a predetermined value, and that I haveprovided for the application of an additional retarding force when the initial predetermined retarding force does not stop the car. It will also be noted thatmy improvement provides for a rapid application of the initial retarding force and a slower application of such additional retarding force as may be necessary to stop the car.

. Since various modifications and changes may be made in the devices illustrated herein as embodying my invention without departing from the spirit and scope thereof, all such modifications and changes are intended to be covered by the appended claims.

I claim as my invention:

1. In a safety device for an elevator, a plurality of safety aws mounted on the car for gripping the guide rails, a pair of levers for operating said jaws, and a safetydrum for actuating said levers, said drum being connected to one lever by a high-pitch screw thread and to the other of said levers by a lower-pitch screw thread.

.2. In a safety device for an elevator, a plurality of safety jaws mounted on the car for gripping the guide rails, a pair of levers for operating said jaws, a safety drum for actuating the presstire-transmitting member to move the lever which it engages, and a low-p1tch screw thread for operating the other of said levers, the frictional engagement between the member and the lever actuated by it being of such degree as to be overcome by the frictional engagement of the high-pitch screw thread and thereby prevent further relative longitudinal move- I ment between the drum and the membe 4:. In a safety device for an elevator, a plurality of safety jaws mounted on the car for gripping the guide rails, a plurality of cooperating levers for operating said jaws, a spring for biasing said jaws toward a closing position, a safety drum for applying positive pressure to said levers, and a pressure-transmitting member disposed between the drum and one of said levers, said member being connected to said lever by a frictional engagement sufficient to prevent the rotation of the member on the lever until the pressure of the biasing spring is overcome.

5. In a safety device for an elevator, a plurality of safety jaws mounted on the car for gripping the guide rails, a plurality of cooperating levers for operating said jaws, a spring for biasing said jaws toward a closing position, a safety drum for applying positive pressure to said levers, and a pressure-transmitting member disposed between the drum and one of said levers, said member being operated by said drum through a screw-threaded connection and being in frictional engagement with its corresponding lever, and said frictional engagement being sufiicient to cause said member to be moved longitudinally by said drum through the screw-threaded connection until the compression of the spring is overcome. 7 v

6. In a safety device for an elevator, a plurality of safety aws mounted on the car for gripping the guide rails, an electromagnet for retaining said jaws in an openposition, an electric circuit controlled by the safety governor for energizing said electromagnet, a spring for actuating said jaws to a closed position when the magnet is deenergized, means for applying additional pressure to said jaws through said spring, and means for applying additional positive pressure to said jaws upon further movement of the car.

7. In a safety device for an elevator, a plurality of safety jaws mounted on the car for gripping the guide rails, an electromagnet for retaining said jaws in an open position, an electric circuit controlled by the safety governor for energizing said electromagnet, a spring for applying a clos ing pressure to said jaws when the magnet is deenergized, means for rapidly applying additional pressure to said jaws through said spring, and means for less rapidly applying additional positive pressure to said jaws upon further movement of the car. i

8. In a safety device for an elevator, a plurality of safety jaws mounted on the car for gripping the guide rails, an electromagnet for retaining said jaws in an open position, an electric circuit controlled by the safety governor for energizing said electromagnet, a spring for applying a closing pressure to said jaws upon deenergization of the electromagnet, a safety drum for applying additional closing pressure to said jaws, a pressure-transmitting member for connecting the drum to the jaws through a frictional engagement, said frictional engagement being calculated to become inoperative upon the application of a predetermined pressure to the spring.

In testimony whereof, I have hereunto subscribed my name this 16th day of April, 1928.

RAY P. HIGBEE. 

